Imagine a future in which the universe will fall apart very soon. Eventually space-time breaks apart, making the universe uninhabitable.
Imagine a future in which the universe will fall apart very soon. First come the clusters whose galaxies are moving away from each other. Later galaxies solve it. Then star systems and planets. And then atoms themselves. Finally, space–time It breaks apart, making the universe uninhabitable.
This is a potential future known as the Big Rip. It sounds scary and almost impossible to imagine, but the truly terrifying part is that some evidence seems to point directly to this fate.
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ghost energy
A quarter of a century ago, astronomers discovered dark energyis the name given to apparent acceleration. expansion of the universe. This dark energy is extremely mysterious; We currently don’t understand what causes it, where it comes from, or what it does. But that hasn’t stopped theorists from making predictions.
The simplest thing dark energy can be is the cosmological constant. In this simple picture, dark energy is a substance that permeates all space and time. There is dark energy everywhere, including the room you are currently in. This dark energy is completely constant. It is exactly the same throughout space and time. This matter causes the expansion of the universe to accelerate, but otherwise it never changes.
Another possibility is that dark energy can cause the matter behind it to double in upon itself and multiply over time. This condition is known as: ghost dark energy (or just ghost energy). In this case, the acceleration will increase over time.
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ghosts in the machine
Ironically, this increase in acceleration would make the observable universe much smaller. This is because the velocity between any two points continues to increase even beyond that point. speed of light. In this scenario, galaxies will fly away from each other so fast that they will never see each other again. This will cause the observable limit of what we can see to shrink uncontrollably over time.
If two points were to be torn apart faster than light, they would no longer be able to interact with any physical force. While a stable dark energy leaves behind already solid objects, such as galaxy clusters, ghost energy can tear them apart. Billions of years from now, over a limited period of time, the clusters will break up, followed by increasingly smaller objects. Even atomic and nuclear bonds cannot withstand this attack.
Eventually, space itself would melt in an event known as the Big Rip. Any two points, no matter how close they are, will forever move away from each other. The structure of space-time, the causal foundations that make our universe work, will no longer function. The universe would collapse.
But luckily, most physicists don’t believe this scenario can actually happen. First of all, it is not clear how this tearing process interacts with other laws of physics. For example, quarks cannot be broken down; When you try to do this, you need so much energy that new quarks emerge from the void. So breaking quarks apart could lead to other interesting interactions.
Additionally, ghost energy does not behave according to normal physics. For this to work, ghost matter must have negative kinetic energy. But negative kinetic energy doesn’t usually occur in the universe – an example of this would be a ball naturally rolling uphill – so this would be a pretty big exception to our established understanding of physics.
Evidence of the Great Rupture
For decades, astronomers have been trying to measure the power of dark energy. They do this through a number known as the state parameter equation, which measures the ratio of its pressure to its energy density for dark energy matter. A cosmological constant corresponds to a parameter equal to -1, while a ghost energy scenario is anything for which this parameter is less than -1.
All astronomical measurements so far are consistent with the cosmological constant, which has a state parameter equation of -1. But oddly enough, year after year, the same measurements favor a value just below -1. All these measurements have uncertainties, including the “boring” state of the cosmological constant, but it is intriguing that the data seem to favor a ghost energy universe.
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Some physicists believe that more evidence will pull us away from the imaginary scenario and into the safety of a cosmological constant. But others see it as a sign that the universe is telling us something interesting. Perhaps there is some combination of physics allowed by current laws that gives the appearance of ghost energy. (For example, if you hit a ball hard enough, it might temporarily go uphill.) Or maybe there’s some brand new physics that seems impossible now but will make sense with new understanding.
But even if we have a ghost energy scenario, it’s not like the universe will fall apart anytime soon. With known measurement limitations, the Great Rip cannot persist for hundreds of billions of years. So in the meantime we can enjoy the beautiful, calm and stable universe.